Can you give an example of a situation where the open/closed principle is violated?

The Open/Closed Principle states that software entities should be open for extension but closed for modification. Violations occur when adding new functionality requires changing existing code.

Example of violation:

Suppose there is a class that calculates delivery cost for different types of products, and to add a new product type, you need to change the method with conditional statements:

class DeliveryCalculator {
    public double calculatePrice(String productType) {
        if (productType.equals("Book")) {
            return 5.0;
        } else if (productType.equals("Electronics")) {
            return 10.0;
        }
        // To add a new product type, this method must be changed
        else if (productType.equals("Furniture")) {
            return 20.0;
        }
        return 0;
    }
}

Here, adding a new product type requires modifying the calculatePrice method, which violates the open/closed principle. A better approach would be to use polymorphism, for example, create a Product interface with a getDeliveryPrice() method, and implement this interface for each product type.